Just freeze the Gel Pack so it is ready to reduce swelling went needed or put the pack in the microwave 30 seconds the warming needed to transmit warmth to the site of an injury. Large 6 x 9 pack stays flexible when frozen and molds to the affected area. Maintains an even temperature either Hot or Cold.keep the reusable Hot and Cold Pack to use over and over again. so it reduces waste and is quickly ready when you need it. Keep it in a the freezer or close to the microwave. (Can also be put in hot water to heat)